The present application is directed to a system of the general type described in U.S. Pat. No. 5,431,061 entitled DEFLECTION TESTING FIXTURE ASSEMBLY AND METHODS OF TESTING issued Jul. 11, 1995, which discloses and claims a system wherein the material being tested must withstand loads which:apply bends in the test panels in two dimensions along two axes simultaneously over a substantial area of surface.
While this machine has proven to work exceedingly well, it has not been possible to use it at much higher pressures to test heavier gauge marine hull multiple plywood and sandwich composite materials or to test more rigid and elongate test panels such as composite material bridge deck samples.
The present mechanism is particularly advantageous for testing the complex interactions between resin, fiber, and core that take place when a flat composite panel is forced to compoundly bend, or between resin and ply when a multi-ply wood sample is so flexed, and differs from the machine depicted in the patent mentioned in certain critical aspects and its ability to operate with more rigid materials.
The present invention is concerned with a machine which can utilize much higher pressures to test not only heavier gauge boat hull composites, but also a host of other rigid composites and other materials which may be used for such diverse purposes as, for example, bridge decks. Such decks may comprise spaced apart flat composite sheets with honeycomb or cellular cores bonding to them as an integral, part of them, and the test panels employed may be elongately rectangular in configuration.
Whereas, in the patent cited, the bladder or envelope was constructed of pliant membranes whose edges were joined in abutting relationship by a perimeter clamp frame, the present bladder incorporates a plate between the membranes with edges which separate the membrane edges and provide an edge composite assembly in which each membrane edge is tightly clamped against the intermediate plate in a manner to seal the bladder so liquid cannot escape, even when the bladder is subjected to pressures in the neighborhood of three times the pressures previously used. The plate stabilizes the clamp frame under these pressures and prevents the clamp frame from distorting out of its footprint and altering the shape of the distributed load during the test.
The prime object of the present invention is to retain the attributes of the previous testing machine, while permitting the machine to apply contact loads on more rigid materials to obtain the required load distributions over the contact areas.